The present invention relates to medical apparatuses and procedures in general, and more particularly to medical apparatuses and procedures for reconstructing a ligament.
In many cases, ligaments are torn or ruptured as the result of an accident. Accordingly, various procedures have been developed to repair or replace such damaged ligaments.
For example, in the human knee, the anterior and posterior cruciate ligaments (i.e., the “ACL” and “PCL”) extend between the top end of the tibia and the bottom end of the femur. Often, the anterior cruciate ligament (i.e., the ACL) is ruptured or torn as the result of, for example, a sports-related injury. Consequently, various surgical procedures have been developed for reconstructing the ACL.
In many instances, the ACL may be reconstructed by replacing the ruptured ACL with a graft ligament. More particularly, in such a procedure, bone tunnels are generally formed in both the top of the tibia and the bottom of the femur, with one end of the graft ligament being positioned in the femoral tunnel and the other end of the graft ligament being positioned in the tibial tunnel, and with the intermediate portion of the graft ligament spanning the distance between the bottom of the femur and the top of the tibia. The two ends of the graft ligament are anchored in their respective bone tunnels in various ways well known in the art so that the graft ligament extends between the bottom end of the femur and the top end of the tibia in substantially the same way, and with substantially the same function, as the original ACL. This graft ligament then cooperates with the surrounding anatomical structures so as to restore substantially normal function to the knee.
Various approaches for anchoring the two ends of the graft ligament in the femoral and tibial bone tunnels are known.
In a known procedure, the end of the graft ligament is placed in the bone tunnel, and then the graft ligament is fixed in place using a headless orthopedic screw, or interference screw. With this approach, the end of the graft ligament is placed in the bone tunnel and then the interference screw is advanced into the bone tunnel so that the interference screw extends parallel to the bone tunnel and simultaneously engages both the graft ligament and the side wall of the bone tunnel. In this arrangement, the interference screw essentially drives the graft ligament laterally, into engagement with the opposing side wall of the bone tunnel, whereby to secure the graft ligament to the host bone with a so-called “interference fit”. Thereafter, over time (e.g., several months), the graft ligament and the host bone grow together at their points of contact so as to provide a strong, natural joinder between the ligament and the bone.
Interference screws have proven to be an effective means for securing a graft ligament in a bone tunnel. However, the interference screw itself generally takes up a substantial amount of space within the bone tunnel, which can limit the extent of contact between the graft ligament and the bone tunnel. This in turn limits the region of bone-to-ligament in-growth, and hence can affect the strength of the joinder. It has been estimated that the typical interference screw obstructs about 50% of the potential bone-to-ligament integration region.
One approach to address this issue is to fabricate the interference screws from bioabsorbable materials, so that the interference screw is absorbed over time and bone-to-ligament in-growth can take place about the entire perimeter of the bone tunnel. In general, this approach has proven clinically successful. However, these absorbable interference screws still suffer from several disadvantages. Clinical evidence suggests that the quality of the bone-to-ligament in-growth is somewhat different than natural bone-to-ligament in-growth, and that the bioabsorbable polymers tend to be replaced by a fibrous mass rather than a well-ordered tissue matrix. Absorption can take a substantial period of time, around three years or so, and during this time, the bone-to-ligament in-growth is still restricted by the presence of the interference screw. In addition, for many patients, absorption is never complete, leaving a substantial foreign mass remaining within the body. This problem is exacerbated somewhat by the fact that absorbable interference screws generally tend to be fairly large in order to provide them with adequate strength, e.g., it is common for an interference screw to have a diameter (i.e., an outer diameter) of 8-12 mm and a length of 20-25 mm.
An alternative approach is disclosed in WO 2008/021474, which describes a composite interference screw for attaching a graft ligament to a bone. The composite interference screw comprises a screw frame for providing the short term strength needed to set the interference screw into position and to hold the graft ligament in position while bone-to-ligament ingrowth occurs, and an ingrowth core for promoting superior bone-to-ligament ingrowth. The screw frame is preferably formed from a bioabsorbable polymer, and the ingrowth core is a bone scaffold structure, also formed from a resorbable polymer, so that the composite interference screw substantially completely disappears from the surgical site over time. The bone scaffold structure may also be an allograft, formed from demineralised bone.
The screw frame includes apertures extending intermediate at least some of the screw threads. Those apertures facilitate contact between the side wall of the bone tunnel and ingrowth core.
It is desirable to utilise an autograft ingrowth core formed from the patient's own bone material. As discussed above, cruciate ligament reconstruction and other similar types of reconstructive surgery require a tendon or graft to be inserted in a bone tunnel. Placement of the tunnel is preferably made at the original attachment site of the ruptured ligament or tendon, and is said to be anatomically placed. The tunnel must have a length sufficient to provide appropriate graft engagement for stiffness and strength. When the bone tunnels are formed the drill findings are not generally collected, and are washed away in the drilling process.
In an alternative approach, the core of bone is harvested for future when the bone tunnel is created. Typically, a surgeon will use a coring trephine system to harvest bone from the patient and this will be used to fill the resultant defect to promote healing. Prior to harvesting the bone, a guide wire is drilled through the bone along the proposed path which the bone tunnel will take. The coring trephine system is cannulated and is slid over the guide wire prior to over-drill the path followed by the guide wire.
A particular problem of the above system is that it is difficult to maintain the trephine corer concentrically, relative to the guide wire. This can be overcome by including additional procedural steps as is described in U.S. Pat. No. 5,423,823 which requires the removal of a guide pin after it has been drilled through the tibia. The introduction of a collared guide pin, and subsequent use of a cannulated core saw. Other systems require additional devices to stabilise the coring reamer while drilling.
However, these systems and methods require additional steps (and devices) to control the trephine while drilling, and thus increase the complexity and time required to carry out the procedure
Accordingly, there exists a need for a better arthroscopic approach.